Analysis Of Hydrochemical Evolution And Applicability Of Groundwater In The People's Victory Canal Irrigation Area

With the continuous exploitation and utilization of groundwater,the hydrochemical evolution of groundwater is becoming more and more complex,and the factors affecting the hydrochemical evolution of groundwater are becoming more and more diverse.How to identify the characteristics and influencing factors of groundwater hydrochemical evolution has become an important and difficult issue in hydrogeology.The People's Victory Canal is the first large-scale irrigation project built in the lower reaches of the Yellow River after the founding of the People's Republic of China.In recent years,with the construction and application of Xiaolangdi reservoir,the water diversion entrance in the irrigation area is restricted by the height of the sluice base,so it is difficult to divert water,the amount of Yellow River diversion decreases,and the amount of groundwater exploitation increases gradually.The change of groundwater dynamic field will cause the change of groundwater chemical field.On the other hand,as the main grain-producing area in Henan province,the large-scale application of chemical fertilizers and pesticides also affects the evolution of the groundwater hydrochemical system.Therefore,this paper analyses the time series change process and spatial distribution of groundwater hydrochemistry,studies the natural and human factors affecting the evolution of groundwater hydrochemistry,and reveals the applicability of groundwater in drinking,agriculture and industry?mainly refers to boiler water?.The purpose of this paper is to provide scientific basis for rational utilization of groundwater and healthy development of water resources system in irrigation area.The main contents and conclusions of this paper are as follows:?1?Based on the cumulative anomaly and inverse distance interpolation method,the spatial distribution and the time series change process of main water chemical components(K⁺,Na⁺,Mg²⁺,Ca²⁺,HCO₃^-,SO₄^2-,Cl^-)and total soluble solids?TDS?in groundwater of the Victory Canal Irrigation Area from 1996 to 2016 were analyzed.In terms of interannual variation,Na⁺and Cl^-show an increasing trend,while SO₄^2-shows a decreasing trend in high TDS areas and an increasing trend in low TDS areas.In terms of annual variation,the high and low TDS areas show different characteristics.The concentration of chemical components in groundwater of low TDS area in the high water period is lower than that in the low water period.Except Na⁺,other ions and TDS increased slightly in high TDS area during the year.?2?Based on correlation analysis and cumulative anomaly analysis,the factors affecting groundwater hydrochemistry were analyzed from two aspects:natural factors?groundwater depth,precipitation,surface water,geological conditions?and human factors?exploitation,planting scale,land use type,human pollution?.The results show that the groundwater in the study area is affected by groundwater depth,precipitation,water diversion from the Yellow River and geological conditions,but the areas with high TDS are less affected by the water diversion from the Yellow River.The change of groundwater exploitation is an important factor that causes the change of groundwater hydrochemistry.Affected by the amount of exploitation,the SO₄^2-concentration in the high TDS area decreases as a whole after 2003,and the TDS decreases gradually,while the SO₄^2-concentration in the low salinity area increases as a whole,and the TDS increases gradually.When the planting area is maintained at a high level,the mean TDS of groundwater in the study area is also maintained at a high level.When the planting area is small,the mean TDS of groundwater in the study area is also at a low level.Land use types have no significant effect on the spatial distribution of groundwater hydrochemistry in the study area.?3?Based on single factor evaluation method,USSL diagram method and Wilcox diagram method,the applicability of groundwater in drinking,irrigation and industry?mainly refers to boiler water?in the study area was evaluated.The results show that the groundwater in the high salinity area of the study area exceeds the standard seriously and is not suitable for drinking water.The main factor leading to the exceeding is salinity.The area unsuitable for drinking water in the study area is gradually expanding to the middle and eastern part of the irrigation area with the change of time.Considering brackish water irrigation,groundwater can be used for irrigation in most areas of the study area,but long-term irrigation may cause salt accumulation in soil.When groundwater is used for boiler water in most areas of the study area,a large number of bubbles and scales will be produced,which is not suitable for direct use as boiler water.